This change introduces pool-aware scheduler to address the need for
supporting multiple pools from one storage controller.
Derived from the Cinder Implementation of Pool-aware Scheduler -
https://review.openstack.org/#/c/98715/ and
https://review.openstack.org/#/c/119938
Implements blueprint: dynamic-storage-pools
Change-Id: I3aee5ed1f96f972f7d40fbd981393559587c1a23